African Journal of Laboratory Medicine最新文献

Background: Patients with faecal carriage of extended-spectrum beta-lactamases (ESBL)-producing Enterobacterales serve as reservoirs and sources of dissemination and infection.

Objective: This report examined immunocompetent patients for faecal carriage of ESBL-producing Enterobacterales in a district care hospital setting in Ghana.

Methods: Between March 2019 and May 2020, cross-sectional sampling was performed to enrol patients and conduct questionnaire-structured interviews for factors that predispose patients to ESBL faecal carriage. Faecal samples from study patients were quantified for ESBL-producing Enterobacterales. The ESBL genes were characterised by polymerase chain reaction and sequencing.

Results: The overall proportion of ESBL faecal carriage was 35.5% (n = 38/107). The bla_CTX-M gene, mostly CTX-M-15, was detected in 89.5% (n = 34/38) of the ESBL-producing isolates. The other ESBL types included bla_SHV (n = 3) and bla_OXA (n = 1). The CTX-M-15-positive isolates, when present in a faecal sample compared to the non-ESBL-CTX-M-15 isolates, constituted the predominant faecal Enterobacterales, with significantly higher colony counts than all other enterobacteria in that sample. In multivariate regression, independent risk factors for faecal carriage of ESBL-producing Enterobacterales were hospitalisation in the past year, infections since admission, use of antibiotics in the past 6 weeks, and admission from another hospital.

Conclusion: The study found that CTX-M-15-producing isolates were the predominant faecal Enterobacterales, and that further investigations are needed to determine the reasons behind this dominance.

What this study adds: The CTX-M-15-producing isolates dominance in this study shows the misuse and abuse of antibiotics in an African medical facility and indicates the potential role of immunity in controlling ESBL spread, which is to be investigated further.

Background: Within the African meningitis belt, yearly outbreaks of cerebrospinal meningitis (CSM), with incidence rates of 10-100 cases per 100 000 population, are typically punctuated by explosive epidemics occurring every 8-12 years, with incidence rates that can exceed 1000 cases per 100 000 population. From 1928 to 2018, Nigeria recorded the highest number (21%) of cases in the region. The reactive vaccination strategy, a protocol with major drawbacks, has been the vaccination method utilised in Nigeria.

Aim: This review highlights the need for governments within the African meningitis belt to start preparations against the next explosive CSM epidemic expected to occur between 2024 and 2028 using the preventive vaccination strategy.

Methods: We performed a literature search on the Google Scholar search engine using relevant search strings and included studies and reports between 1905 and 2022 that met set criteria.

Results: Neisseria meningitidis serogroups A, B, C, W135, X, and Y; Haemophilus influenzae serotypes a, b, c, e, and f; and Streptococcus pneumoniae serotypes 1, 4, 5, 6, 9, 19, 19F, and 20 were implicated as aetiologies. However, the reactive vaccination strategy was only used against N. meningitidis A or C, H. influenzae b, and pneumococcal conjugate vaccine. Between 2011 and 2017, a polysaccharide vaccine (ACW or ACYW) active against serogroups A, C, W and Y was used within the African meningitis belt for the first time. Varying genotypes of N. meningitidis, H. influenzae and S. pneumoniae were identified.

Conclusion: Our results revealed a very high success rate for the preventive vaccination strategy.

What this study adds: In order to ensure reductions in the morbidity and mortality associated with invasive CSM, the Federal Ministry of Health, Nigeria, should leverage existing knowledge of the circulating serogroups, serotypes, and genotypes of the primary bacterial aetiologies and commence the implementation of the preventive vaccination strategy.

Background: All medical laboratories must participate in proficiency testing (PT) programmes to ensure high-quality results. Proficiency testing samples mimic clinical samples; however, PT programmes for detection of bacteria in blood products are not routinely performed due to unavailability of matrix-equivalent samples.

Objective: The aim of this study was to develop and test a matrix-equivalent PT programme using blood products as the basis matrix.

Methods: A prospective cross-sectional study was conducted from April 2021 until June 2021, using 52 blood products comprising 36 pooled platelet and 16 red blood cell products at the South African National Blood Service PT laboratory in Gauteng. Products were manipulated into matrix-equivalent PT samples by spiking 42 products with known bacterial strains at specific concentrations and treating the remaining 10 products with preserving fluid containing antibiotics. The level of agreement between the researcher results and participating laboratories' results was assessed.

Results: Of the prepared matrices, 568 out of 572 (99%) were stable for 30 days. Bacteria could correctly be identified in spiked samples for up to 23 days. Samples treated with preserving fluid remained negative until day 30. For spiked samples, an average of 98% agreement (153/156) was achieved between the three participating laboratories when compared with the researcher's results; 100% agreement was achieved for unspiked samples. The kappa scores obtained from all tested variables presented with scores between 0.856 and 1.000, and the p-value was < 0.001 throughout.

Conclusion: The developed PT matrix was therefore stable and suitable to be implemented in transfusion microbiology.

What this study adds: This study demonstrated that a stable microbiology PT programme using platelets and red blood cells can be developed for use on bacterial detection analysers and could help to close the gap presented by unavailability of a blood PT matrix for transfusion microbiology.

Background: Integrated testing, treatment and care are key strategies for addressing the dual burdens of tuberculosis and HIV. The GeneXpert instrument allows simultaneous HIV and tuberculosis testing, but its utilisation for integrated testing remains suboptimal.

Objective: The study determined the extent to which tuberculosis testing and HIV early infant detection (EID) were integrated on the GeneXpert platform, or the potential for integration at selected health facilities.

Methods: A mixed methods evaluation was conducted using retrospective secondary data analysis of laboratory records from 2017 to 2019, and semi-structured interviews. Data were collected between January 2020 and March 2020 in Lesotho.

Results: Forty-four health staff were interviewed across 13 health facilities: one regional, nine district, and three clinic level. Six were government facilities, six were mission hospitals, and one was a non-profit clinic. All facilities selected had at least one GeneXpert instrument used for tuberculosis or HIV testing; none included simultaneous testing for tuberculosis and HIV. In 2017, the average utilisation rate for the GeneXpert instrument for tuberculosis and EID testing was 63% and 24%, while in 2019, the average utilisation rate was 61% for tuberculosis testing and 27% for EID.

Conclusion: Except for three sites where the testing rates were high, utilisation rates were sufficiently low that all the HIV EID and tuberculosis tests undertaken in 2017 and 2019 could have been performed using only the instruments currently dedicated to tuberculosis testing. There is a missed opportunity for the integration of testing for tuberculosis and HIV on the GeneXpert instrument.

What this study adds: This study adds to the body of evidence on the need for integration of testing and highlights some practical and technical considerations for successful implementation of integrated tuberculosis and HIV testing.

Background: Integrated diagnostic networks, which are themselves dependent on robust specimen transport solutions, are fundamental to effective healthcare systems.

Objective: This study aimed to pilot an online marketplace for the transport of specimens throughout a laboratory network in Ghana.

Methods: Independent drivers were matched with health facilities that required specimen transport using a suite of mobile applications and web portals developed for this study. This marketplace was piloted with seven drivers, two laboratories, and five health facilities in Ghana's Northern region from March 2019 to October 2019.

Results: During the pilot, 182 deliveries were completed for 691 patients, including 4118 laboratory tests for antenatal care, disease surveillance, and clinical testing. Testing included 34 tests for communicable and non-communicable diseases. All but two specimens (laboratory cancellations) were successfully delivered and tested. The median time from request to encrypted emailing of results was 19.7 h, while that for a drop-off request was 0.9 h. In the midwife registry, the median time from patient visit to result recording was 1 day, compared to 4 days in the same months in 2018, and the number of mothers without documented testing decreased from 41 to 3. Similarly, the proportion of tuberculosis specimen deliveries from Buipe Polyclinic to Tamale Zonal Laboratory taking over 1 day fell from 62% at baseline to 3% during the pilot.

Conclusion: An online marketplace successfully orchestrated the delivery of laboratory specimens under a variety of clinical circumstances, reducing overall turn-around time without diminution of the overall specimen delivery process.

What this study adds: This study established the efficacy of an online marketplace to orchestrate timely and high-quality delivery of specimens within a laboratory network.

Background: Automated haematology analysers such as the Sysmex XN-3000 (Sysmex Corporation, Kobe, Japan) utilise white blood cell (WBC) flags to identify quantitative and qualitative abnormalities. Owing to clinical and biological factors, the sensitivity and specificity of the flags vary when compared to microscopy, the gold-standard method for assessing peripheral blood smear (PBS) morphology.

Objective: This study assessed the performance of the Sysmex XN-3000 haematology analyser in comparison to PBS microscopy for the detection of WBC abnormalities.

Methods: We collected 250 random full blood count samples from the haematology laboratory at Inkosi Albert Luthuli Central Hospital, Durban, KwaZulu-Natal, South Africa, from March 2022 to April 2022. The performance of the automated WBC flags of the Sysmex XN-3000 was assessed in comparison to PBS microscopy, and the impact of established clinical variables on the performance of the flags was determined.

Results: The sensitivity of the 'blast' flag was 96.3%, and the specificity was 84.9%. The efficiency of the flag was adversely impacted by low white cell counts (< 1.5 × 10⁹/L; p < 0.001), chemotherapy (p = 0.002), malignancy (p = 0.02), and infection (p = 0.02). The 'abnormal lymphocyte' flag demonstrated a sensitivity of 90% and a specificity of 96.2%, and its performance was adversely impacted by chemotherapy exposure (p = 0.03). Three cases (1.2%) erroneously flagged as 'monocytosis' demonstrated blasts on microscopy.

Conclusion: In our setting, PBS microscopy remains necessary to confirm blasts, abnormal lymphocytes, and monocytosis in patients with malignancy, current chemotherapy exposure, low white cell counts, and infection.

What this study adds: This study adds evidence that PBS morphology remains the gold standard for confirming WBC abnormalities in patients with a history of malignancy, chemotherapy, and leucopenia.

Antimicrobial resistance in methicillin-resistant Staphylococcus aureus and beta-lactamase-producing Gram-negative bacteria is a global health concern necessitating research and the development of effective antimicrobial agents. This study, conducted in May 2020 in Mwanza, Tanzania, aimed to determine the antibacterial activity of metabolites from soil-isolated Bacillus species against clinical bacterial pathogens. One soil-isolated Bacillus species, identified as Bacillus altitudinis/pumilus complex, showed antibacterial activity against Gram-positive cocci, including a methicillin-resistant S. aureus strain with inducible clindamycin resistance, previously isolated from a patient with osteomyelitis. Bacillus altitudinis/pumilus complex metabolites may be a potential source of antimicrobial agents against multidrug-resistant bacteria.

What this study adds: The study supports existing research on the discovery and development of new antimicrobial agents against multi-drug-resistant bacteria. We report the antimicrobial activity of metabolites extracted from soil-isolated Bacillus altitudinis/pumilus complex strains against Gram-positive bacteria, including a methicillin-resistant Staphylococcus aureus strain with inducible clindamycin resistance.